Doppler Effect and Redshift Wave Properties Recall that the wavelength is the distance between two peaks. Wave Properties

Frequency (f)-the number of waves passing a particular point in one second

● Longer wavelength=lower frequency ● Shorter wavelength=higher frequency Doppler Effect

● When there is relative motion between a source and an observer the Doppler Effect occurs. ○ Motion towards each other=higher frequency. A higher pitch is heard by the observer. ○ Motion away from each other=lower frequency. A lower pitch is heard by the observer ○ The Doppler effect can be observed in any type of wave: water wave, sound wave, light wave Doppler Effect

Explain the following visual. How might the sounds be different? Doppler Effect Electromagnetic Waves

● Recall that light behaves as a wave. ● How might light detected from a star that is moving away from an observer be different that the light detected from a star moving toward an observer? Redshift

● Occurs when a light emitting object is moving away from an observer. This might be a star or a galaxy in our case. ● The wavelength of light emitted is stretched out. ● This shifts the light towards the longer wavelengths of the spectrum-ie: red. Hubble’s Discovery

•Hubble observed that the wavelength of light coming from distant galaxies was experiencing redshift . •This means the light source is moving away from the observer and increasing in wavelength (doppler effect). •The longer the light travels, the more it gets redshifted

How does this information support our theory that the Universe is expanding?